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ofb128.c 2.4 KB

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  1. /*
  2. * Copyright 2008-2021 The OpenSSL Project Authors. All Rights Reserved.
  3. *
  4. * Licensed under the Apache License 2.0 (the "License"). You may not use
  5. * this file except in compliance with the License. You can obtain a copy
  6. * in the file LICENSE in the source distribution or at
  7. * https://www.openssl.org/source/license.html
  8. */
  9. #include <string.h>
  10. #include <openssl/crypto.h>
  11. #include "crypto/modes.h"
  12. #if defined(__GNUC__) && !defined(STRICT_ALIGNMENT)
  13. typedef size_t size_t_aX __attribute((__aligned__(1)));
  14. #else
  15. typedef size_t size_t_aX;
  16. #endif
  17. /*
  18. * The input and output encrypted as though 128bit ofb mode is being used.
  19. * The extra state information to record how much of the 128bit block we have
  20. * used is contained in *num;
  21. */
  22. void CRYPTO_ofb128_encrypt(const unsigned char *in, unsigned char *out,
  23. size_t len, const void *key,
  24. unsigned char ivec[16], int *num, block128_f block)
  25. {
  26. unsigned int n;
  27. size_t l = 0;
  28. if (*num < 0) {
  29. /* There is no good way to signal an error return from here */
  30. *num = -1;
  31. return;
  32. }
  33. n = *num;
  34. #if !defined(OPENSSL_SMALL_FOOTPRINT)
  35. if (16 % sizeof(size_t) == 0) { /* always true actually */
  36. do {
  37. while (n && len) {
  38. *(out++) = *(in++) ^ ivec[n];
  39. --len;
  40. n = (n + 1) % 16;
  41. }
  42. # if defined(STRICT_ALIGNMENT)
  43. if (((size_t)in | (size_t)out | (size_t)ivec) % sizeof(size_t) !=
  44. 0)
  45. break;
  46. # endif
  47. while (len >= 16) {
  48. (*block) (ivec, ivec, key);
  49. for (; n < 16; n += sizeof(size_t))
  50. *(size_t_aX *)(out + n) =
  51. *(size_t_aX *)(in + n)
  52. ^ *(size_t_aX *)(ivec + n);
  53. len -= 16;
  54. out += 16;
  55. in += 16;
  56. n = 0;
  57. }
  58. if (len) {
  59. (*block) (ivec, ivec, key);
  60. while (len--) {
  61. out[n] = in[n] ^ ivec[n];
  62. ++n;
  63. }
  64. }
  65. *num = n;
  66. return;
  67. } while (0);
  68. }
  69. /* the rest would be commonly eliminated by x86* compiler */
  70. #endif
  71. while (l < len) {
  72. if (n == 0) {
  73. (*block) (ivec, ivec, key);
  74. }
  75. out[l] = in[l] ^ ivec[n];
  76. ++l;
  77. n = (n + 1) % 16;
  78. }
  79. *num = n;
  80. }